The present invention relates to a keyhole button used as replenishment for a keyhole portion of a cranium formed when trepanation of the frontal or temporal bone is performed in the field of cranial nerve surgery. More particularly, the present invention relates to a keyhole button, which is superior in the adaptability to an organism, and in the stability, and does not disfigure the appearance of face after the operation is performed.
Conventionally, many craniotomy operations and closing operations have been performed in the field of cranial nerve surgery. Generally, a craniotomy operation includes following steps:
incising a head skin and exposing a cranium;
making some fossae on a cranium by a drill in accordance with a size and a region of the portion to be trepanned;
cutting between the fossae by a line saw;
taking out a bone flap; and
dissecting an internal dura mater.
In this operation, a portion at which a fossa is firstly made by drilling is located near the temple, and is called a xe2x80x9ckeyhole.xe2x80x9d
The shape of the keyhole portion varies depending on the shape of the bone of individual patient and/or a doctor who performs the operation. Accordingly, it has been difficult to make a standard product of a bone substitute (which is referred to as a keyhole button). Conventionally, when the craniotomy has been performed, resin is filled into the keyhole portion as the supplemental member. However, there is a problem in adaptability to an organism and fever thereof. Recently, the keyhole buttons made of calcium phosphate compound, which has bio-compatibility, or adaptability to an organism, are used in some cases. However, such keyhole buttons have a stability problem and/or an appearance problem since the keyhole button does not match the shape around the keyhole portion.
It is therefore an object of the present invention to provide an improved keyhole button, which has high adaptability to an organism and stability, and further, with which the appearance of the face after the operation is performed is not disfigured.
For the above object, according to the present invention, there is provided a keyhole button used as a supplement of a keyhole portion formed on a cranium. The keyhole button is constituted to have a brim portion having front and back surfaces, and a shaft portion integrally provided on the back surface of said brim portion. The front surface of the brim portion is convexed in a first direction, and concaved in a second direction that is perpendicular to the first direction. Thus, the keyhole button functions as an excellent bone supplement in view of the adaptability to an organism, stability, and an appearance after the operation.
Preferably, the shaft portion is substantially cylindrical.
Further, the brim portion has a rounded-rectangular shape having longer axis and shorter axis, the longer axis extending in said first direction, the shorter axis extending in said second direction. Furthermore, the center of said shaft portion is shifted from the center of said brim portion in said first direction.
Still optionally, a peripheral portion on said front surface of said brim portion is beveled.
It is preferable that the keyhole button is made of porous calcium phosphate compound. In this case, it is preferable that the porosity of said keyhole button is 55% or less.
Further optionally, the keyhole button is formed of porous sinter material. Since the keyhole button is formed of the porous material, the brim portion can be shaped relatively easily by sintering, the thickness of the brim portion can be made relatively small.